This is a multimodal, nonrandomized study of healthy subjects. After meeting enrollment criteria, subjects will receive a baseline neurocognitive testing on a computer for 15 minutes and will then receive a wrist watch actigraphy device to record their rest/activity patterns over 8-14 days. On the study day (roughly two weeks later), repeat baseline neurocognitive testing will be performed after subjects are fitted with a high density EEG head cap. The actual intervention (delivery of inhaled xenon gas in stepwise increasing followed by decreasing doses) should occur over 4 hours along with verbal tests to assess the presence/absence of consciousness at each xenon concentration. Xenon doses have been chosen specifically to evaluate the point at which individuals lose and then regain consciousness. Doses are escalated up through those used in human anesthesiology (75%) that permit surgery. After exposure, serial neurocognitive testing will occur every 30 minutes for 3 hours post emergence. Subjects are discharged from the study's intervention day to home only upon reaching standard post-anesthesia care unit criteria (modified Aldrete score ≥9). A post-procedure follow up phone call will occur within 24 hours of anesthetic exposure to ensure that the subject remains well. The individual's involvement is completed upon returning the Actigraphy watch 1 week after the exposure day. The expected duration of subject participation is 3 weeks.